Turbocharging Photosynthesis to Feed the World

A faster enzyme for turning CO2 into sugar is a key step toward much higher crop yields.

Yields of wheat are increasing at 1 percent per year—half the rate of increase needed to keep the world fed.

Two down, one to go. Researchers have completed the second of three major steps needed to turbocharge photosynthesis in crops such as wheat and rice, something that could boost yields by around 36 to 60 percent for many plants. Because it’s more efficient, the new photosynthesis method could also cut the amount of fertilizer and water needed to grow food.

This tobacco plant uses genes taken from bacteria for photosynthesis.

Researchers at Cornell University and Rothamsted Research in the United Kingdom successfully transplanted genes from a type of bacteria—called cyanobacteria—into tobacco plants, which are often used in research. The genes allow the plant to produce a more efficient enzyme for converting carbon dioxide from the atmosphere into sugars and other carbohydrates. The results are published today in the journal Nature.

Scientists have long known that some plants are much more efficient at turning carbon dioxide into sugar than other plants. These fast-growing plants—called C4 plants—include corn and many types of weeds. But 75 percent of the world’s crops (known as C3 plants) use a slower and less efficient form of photosynthesis. Researchers have been attempting for a long time to change some C3 plants—including wheat, rice, and potatoes—into C4 plants. The approach has been given a boost lately by novel high-precision gene-editing technologies that are being applied to the C4 Rice Project (see “Why We Will Need Genetically Modified Foods”).

The Cornell and Rothamsted researchers took a simpler approach. Rather than attempting to convert a C3 plant into a C4 plant by changing its anatomy and adding new cell types and structures, the researchers modified components of existing cells. “If you can have a simpler mechanism that doesn’t require anatomical changes, that’s pretty darn good,” says Daniel Voytas, director of the Center for Genome Engineering at the University of Minnesota.

Instead of mimicking C4 plants, the researchers borrowed a three-part photosynthesis mechanism from cyanobacteria. First, proteins form a special compartment within a plant cell that concentrates CO2; second, the compartment contains a speedy enzyme for converting that CO2; and third, the cells use special pumps in their membranes to usher CO2 into the cells.

Earlier this year, the researchers engineered cells to form the special CO2 compartments. The new research takes care of the second part—the speedy enzyme. They’re collaborating with other researchers on the third part, the pumps. Ultimately the researchers will need to put all three parts together in the same plants.

Maureen Hansen, a professor of molecular biology and genetics at Cornell, says the advances won’t be seen in commercially grown food crops for at least five or 10 years.

To do that won’t be a simple matter of transplanting one or two genes. It will require transferring 10 to 15 genes, and making sure the genes are stable, says Dean Price, a professor of medicine, biology, and environment at Australian National University. Price was not involved in the current research. Only then can extensive field testing begin, along with the regulatory process for genetically modified crops.

The approach will likely be limited at first to a few plants that researchers are particularly good at genetically modifying, such as potatoes, tomatoes, eggplant, and peppers. However, Price says, there are genetic workarounds that could quickly make it possible in a wider range of crops.